> -----Original Message----- > From: owner-linux-mm@xxxxxxxxx [mailto:owner-linux-mm@xxxxxxxxx] On > Behalf Of Tycho Andersen > Sent: Thursday, September 7, 2017 10:36 AM > To: linux-kernel@xxxxxxxxxxxxxxx > Cc: linux-mm@xxxxxxxxx; kernel-hardening@xxxxxxxxxxxxxxxxxx; Marco Benatto > <marco.antonio.780@xxxxxxxxx>; Juerg Haefliger > <juerg.haefliger@xxxxxxxxxxxxx>; x86@xxxxxxxxxx; Tycho Andersen > <tycho@xxxxxxxxxx> > Subject: [PATCH v6 03/11] mm, x86: Add support for eXclusive Page Frame > Ownership (XPFO) > > From: Juerg Haefliger <juerg.haefliger@xxxxxxxxxxxxx> > > This patch adds support for XPFO which protects against 'ret2dir' kernel attacks. > The basic idea is to enforce exclusive ownership of page frames by either the > kernel or userspace, unless explicitly requested by the kernel. Whenever a page > destined for userspace is allocated, it is unmapped from physmap (the kernel's > page table). When such a page is reclaimed from userspace, it is mapped back to > physmap. > > Additional fields in the page_ext struct are used for XPFO housekeeping, > specifically: > - two flags to distinguish user vs. kernel pages and to tag unmapped > pages. > - a reference counter to balance kmap/kunmap operations. > - a lock to serialize access to the XPFO fields. > > This patch is based on the work of Vasileios P. Kemerlis et al. who published their > work in this paper: > http://www.cs.columbia.edu/~vpk/papers/ret2dir.sec14.pdf > > v6: * use flush_tlb_kernel_range() instead of __flush_tlb_one, so we flush > the tlb entry on all CPUs when unmapping it in kunmap > * handle lookup_page_ext()/lookup_xpfo() returning NULL > * drop lots of BUG()s in favor of WARN() > * don't disable irqs in xpfo_kmap/xpfo_kunmap, export > __split_large_page so we can do our own alloc_pages(GFP_ATOMIC) to > pass it > > CC: x86@xxxxxxxxxx > Suggested-by: Vasileios P. Kemerlis <vpk@xxxxxxxxxxxxxxx> > Signed-off-by: Juerg Haefliger <juerg.haefliger@xxxxxxxxxxxxx> > Signed-off-by: Tycho Andersen <tycho@xxxxxxxxxx> > Signed-off-by: Marco Benatto <marco.antonio.780@xxxxxxxxx> > --- > Documentation/admin-guide/kernel-parameters.txt | 2 + > arch/x86/Kconfig | 1 + > arch/x86/include/asm/pgtable.h | 25 +++ > arch/x86/mm/Makefile | 1 + > arch/x86/mm/pageattr.c | 22 +-- > arch/x86/mm/xpfo.c | 114 ++++++++++++ > include/linux/highmem.h | 15 +- > include/linux/xpfo.h | 42 +++++ > mm/Makefile | 1 + > mm/page_alloc.c | 2 + > mm/page_ext.c | 4 + > mm/xpfo.c | 222 ++++++++++++++++++++++++ > security/Kconfig | 19 ++ > 13 files changed, 449 insertions(+), 21 deletions(-) > > diff --git a/Documentation/admin-guide/kernel-parameters.txt > b/Documentation/admin-guide/kernel-parameters.txt > index d9c171ce4190..444d83183f75 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -2736,6 +2736,8 @@ > > nox2apic [X86-64,APIC] Do not enable x2APIC mode. > > + noxpfo [X86-64] Disable XPFO when CONFIG_XPFO is on. > + > cpu0_hotplug [X86] Turn on CPU0 hotplug feature when > CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off. > Some features depend on CPU0. Known dependencies <... snip> A bit more description for system administrators would be very useful. Perhaps something like: noxpfo [XPFO,X86-64] Disable eXclusive Page Frame Ownership (XPFO) Physical pages mapped into user applications will also be mapped in the kernel's address space as if CONFIG_XPFO was not enabled. Patch 05 should also update kernel-parameters.txt and add "ARM64" to the config option list for noxpfo. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href
